# AQA Physics 3 Q&A

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• Created on: 09-05-12 17:43

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Physics P3
End of Unit Questions – Answers

P3-1 : Moments

What is the moment of a force?

A moment is defined as the turning effect of a force, which depends on the distance between the point where the force is being applied and the strength of the force applied

How do you work out a moment?

A moment is calculated using the following equation: moment = force x perpendicular distance from pivot

What is another name for the centre of mass?

Centre of gravity

Explain non-equilibrium

When an object is being suspended and is to one side, the centre of mass will not be directly below the point of suspension, so the object is said to be in non-equilibrium

Explain the Principle of Moments

The Principle of Moments stated that the sum of all moments clockwise around a point is equal to the sum of all anticlockwise moments around that same point

What makes an object topple?

A tilted object will only topple when released if the “line of action” is outside its base

Explain the difference between circular motion and centripetal force

Circular motion is the act of an object travelling around in a circular direction, whereas centripetal force is the idea of the force of the moment always acting towards the centre of the circle

Define the terms: load, effort and pivot

In a lever-style moment, the load is the weight being lifted, the effort is the force being applied and the pivot is the point around which the lifter lifts the weight

What is meant by the centre of mass?

If the weight of an object were to act at a single point, this is the centre of mass

When is an object in equilibrium?

A suspended object is in equilibrium when its centre of mass is directly below the point of suspension in the air

Where is the centre of mass for a rectangle?

Rectangles have two four lines of symmetry and these all cross at a single point in the centre of the rectangle. The point at which the axes all cross is where the centre of mass is

Explain how a tractor has been adapted to stay upright

The centre of mass for a tractor is in its engine which is deliberately low and close to the ground to give it a low centre of mass. This means that the tractor will have to tilt more to topple over. It also has a wide wheel base to decrease risk of toppling

What is circular motion?

An object which constantly moves around in a circle goes through circular motion, where the object’s velocity is directed at a tangent to the circle

Name Newton’s laws of gravity

Newton said that the force of gravity between two objects is an attractive force; increases when object mass increases; and decreases with distance between the objects

Define gravitational field strength

The gravitational field strength refers to the

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